This biological account was modified from Sammataro et al., 2000.
Several key morphological features help make Varroa a successful ectoparasite: It can survive off the host for 18 to 70 hours, depending on the substrate; the female’s chelicerae are structurally modified — the fixed digit is lacking and the moveable digit is a saw-like blade capable of piercing and tearing the host’s integument; the mite’s body is dorsoventrally compressed, allowing the mite to fit beneath the bee’s abdominal sclerites, thus lessening water loss from transpiration; and hiding there reduces Varroa’s vulnerability to grooming and to dislodgment during host activity.
Varroa females are often found on adult bees, which provide for dispersal and serve as short-term hosts. Varroa prefers young bees to older workers, probably because of the lower titer of the Nasonov gland pheromone geraniol, which strongly repels the mite. The mite pierces the soft intersegmental tissues of the bee’s abdomen or behind the bee’s head, and feeds on the hemolymph. When in an actively reproducing bee colony, the mite disembarks and seeks brood cells containing third-stage bee larvae. Varroa, which prefers drone larvae but also invades workers’ cells, is attracted to fatty acid esters, which are found in higher quantities on immature drones than on workers. Other known attractants are the aliphatic alcohols and aldehydes from bee cocoons and perhaps the larger volume of drone cells.
Most species in this genus are relatively benign parasites associated with honey bees in the wild. However, one species, Varroa destructor, has spread from Apis cerana to Apis mellifera, causing enormous bee losses. Varroa destructor can kill entire colonies of its unnatural host, the European honey bee Apis mellifera, while it does not kill colonies of its natural host, Eastern honey bee Apis cerana. This difference may be due to the presence of resistance against the mite developed by Apis cerana over evolutionary time.